The overall objective of this proposal is to understand better how some of the variables such as taste and signals arising from the gastrointestinal tract interact during a meal to determine its size. The experimental approach used here measures the rate of occurrence of the rhythmic tongue movements that occur in rats when they are ingesting liquid diets. This approach allows the investigator to examine how the pattern of this licking behavior changes from the beginning of the meal to the end, and, thus to track the influence of variables that come into play at different times during the meal to modify its size. The use of this method has led to the discovery that meal size is controlled in part by a mechanism dependent upon an association between taste of the test diet and its post gastric consequences. This inhibition is revealed as a progressive increase in the rate of ingestion early in a meal when rats are given experience ingesting a liquid diet that does not stimulate the post gastric compartment. The end result is a significant increase in the size of the meals. The aims of this proposal are to study this phenomenon in detail to attempt to determine the nature of the post gastric signal(s) and the pathway or pathways by which this information is conveyed to the central nervous system. This will be achieved by manipulating post gastric stimulation independent of that the animal is eating and by severing some of the afferent pathways from the gastrointestinal tract to the brain. An understanding of the types of signals that participate in the normal control of the amount of food that is ingested in a meal and their mode of action in normal animals is essential to a better understanding of the pathologies such as anorexia and bulemia that can occur and to a better understanding of the problem of obesity.